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Document and Entity Information - $ / shares	3 Months Ended
Document and Entity Information - $ / shares	Mar. 31, 2014	May 01, 2014
Document and Entity Information
Entity Registrant Name	Esperion Therapeutics, Inc.
Entity Central Index Key	0001434868
Document Type	10-Q
Document Period End Date	Mar. 31, 2014
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Non-accelerated Filer
Entity Common Stock, Shares Outstanding		15,394,226
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	Q1
Entity Listing, Par Value Per Share	$ 0.001

Condensed Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 48,638	$ 56,537
Short-term investments	8,064	3,525
Prepaid clinical development costs	1,257	196
Other prepaid and current assets	320	362
Total current assets	58,279	60,620
Property and equipment, net	360	81
Intangible assets	56	56
Investments	11,528	17,537
Total assets	70,223	78,294
Current liabilities:
Accounts payable	2,098	2,232
Accrued clinical development costs	526	884
Other accrued liabilities	564	1,087
Total current liabilities	3,188	4,203
Total liabilities	3,188	4,203
Commitments and contingencies (Note 5)
Stockholders' equity:
Preferred stock, $0.001 par value; 5,000,000 shares authorized as of March 31, 2014 and December 31, 2013; no shares issued or outstanding at March 31, 2014 and December 31, 2013
Common stock, $0.001 par value; 120,000,000 shares authorized as of March 31, 2014 and December 31, 2013; 15,394,226 shares issued and 15,379,311 outstanding at March 31, 2014 and 15,357,413 shares issued and 15,340,710 outstanding at December 31, 2013	15	15
Additional paid-in capital	142,954	142,142
Accumulated other comprehensive income	3	(3)
Deficit accumulated during the development stage	(75,937)	(68,063)
Total stockholders' equity	67,035	74,091
Total liabilities and stockholders' equity	$ 70,223	$ 78,294

Condensed Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2014	Dec. 31, 2013
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	15,394,226	15,357,413
Common stock, shares outstanding	15,379,311	15,340,710

Condensed Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		74 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Condensed Statements of Operations and Comprehensive Loss
Grant income			$ 244
Operating expenses:
Research and development	$ 5,400	$ 2,093	48,828
General and administrative	2,490	1,251	20,684
Acquired in-process research and development			86
Total operating expenses	7,890	3,344	69,598
Loss from operations	(7,890)	(3,344)	(69,354)
Interest expense		(828)	(4,321)
Change in fair value of warrant liability	0	(42)	(2,554)
Other income (expense), net	16	(25)	292
Net loss	$ (7,874)	$ (4,239)	$ (75,937)
Net loss per common share (basic and diluted) (in dollars per share)	$ (0.51)	$ (12.24)
Weighted-average shares outstanding (basic and diluted)	15,369,055	346,478
Other comprehensive income:
Unrealized gain on investments	$ 3
Total comprehensive loss	$ (7,871)	$ (4,239)

Condensed Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		74 Months Ended
Condensed Statements of Cash Flows - USD ($) $ in Thousands	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Operating activities
Net loss	$ (7,874)	$ (4,239)	$ (75,937)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	12	32	1,460
Amortization of debt discount and beneficial conversion		459	576
Amortization of debt issuance costs		19	34
Amortization of premiums and discounts on investments	53		100
Revaluation of warrants	0	42	2,554
Noncash interest expense on convertible notes		351	3,726
Write-off of acquired in-process research and development			86
Stock-based compensation expense	741	55	2,225
Common stock issued in license agreement			4
Loss related to assets held for sale	6	27	329
(Gain)/Loss on sale of assets	11	(1)	(155)
Changes in assets and liabilities:
Prepaids and other assets	(1,028)	(656)	(1,537)
Accounts payable	(159)	450	2,073
Other accrued liabilities	(866)	834	1,030
Net cash used in operating activities	(9,104)	(2,627)	(63,432)
Investing activities
Purchases of investments	(3,000)		(59,246)
Proceeds from sales/maturities of investments	4,426		39,446
Cash obtained in stock acquisition			2,500
Proceeds from sale of assets		1	952
Purchase of property and equipment	(273)		(572)
Other investing			51
Net cash (used in) provided by investing activities	1,153	1	(16,869)
Financing activities
Proceeds from initial public offering, net of issuance costs			72,194
Proceeds from issuance of preferred stock, net of issuance costs			40,799
Proceeds from exercise of common stock options	52		236
Proceeds from warrant issuance			298
Proceeds from debt issuance with related parties			15,412
Net cash provided by financing activities	52		128,939
Net increase (decrease) in cash and cash equivalents	(7,899)	(2,626)	48,638
Cash and cash equivalents at beginning of period	56,537	6,512
Cash and cash equivalents at end of period	$ 48,638	3,886	48,638
Convertible promissory note
Supplemental disclosure of cash flow information:
Conversion of convertible promissory notes, including accrued interest of $923 into Series A preferred stock		$ 16,623	16,623
Pfizer note
Supplemental disclosure of cash flow information:
Conversion of convertible promissory notes, including accrued interest of $923 into Series A preferred stock			$ 7,803

Condensed Statements of Cash Flows (Parenthetical) $ in Thousands	Mar. 31, 2014 USD ($)
Convertible promissory note
Conversion of convertible promissory notes into preferred stock, accrued interest	$ 923
Pfizer note
Conversion of convertible promissory notes into preferred stock, accrued interest	$ 274

The Company and Basis of Presentation

3 Months Ended

Mar. 31, 2014

The Company and Basis of Presentation

The Company and Basis of Presentation

1. The Company and Basis of Presentation

The Company is a clinical stage biopharmaceutical company focused on developing and commercializing first in class, oral, low density lipoprotein cholesterol (LDL-C) lowering therapies for the treatment of patients with hypercholesterolemia and other cardiometabolic risk markers. ETC-1002, the Company’s lead product candidate, is a unique, first in class, orally available, once daily small molecule designed to lower LDL-C levels and avoid the side effects associated with currently available LDL-C lowering therapies. ETC-1002 is being developed primarily for patients intolerant of statins with elevated levels of LDL-C. Phase 2b clinical trials for ETC-1002 are currently underway and build upon a successful and comprehensive Phase 1 and Phase 2 program. The Company owns the exclusive worldwide rights to ETC-1002 and its other product candidates.

HDL Therapeutics, Inc. (HDL) was incorporated in the state of Delaware on January 22, 2008. On April 28, 2008, HDL acquired all of the capital stock of Esperion Therapeutics, Inc. (Esperion), a wholly owned subsidiary of Pfizer Inc. On May 5, 2008, Esperion was merged with and into HDL and the Company assumed the name Esperion Therapeutics, Inc. (the Company). Its facilities are located in Ann Arbor and Plymouth, Michigan.

The Company’s primary activities since incorporation have been recruiting personnel, conducting research and development activities, including nonclinical and clinical testing, performing business and financial planning, and raising capital. Accordingly, the Company is considered to be in development stage.

The Company is subject to the risks associated with a development stage entity, which includes the need to research, develop, and clinically test potential therapeutic products; obtain regulatory approvals for its products and commercialize them, if approved; expand its management and scientific staff; and finance its operations with an ultimate goal of achieving profitable operations.

The Company has sustained operating losses since inception and expects such losses to continue over the foreseeable future. Management plans to continue to finance operations with a combination of public and private equity issuances, debt arrangements, collaborations and strategic and licensing arrangements. If adequate funds are not available, the Company may not be able to continue the development of its current or future product candidates, or to commercialize its current or future product candidates, if approved.

Basis of Presentation

The accompanying condensed financial statements are unaudited and were prepared by the Company in accordance with generally accepted accounting principles in the United States of America (GAAP). In the opinion of management, the Company has made all adjustments, which include only normal recurring adjustments necessary for a fair statement of the Company’s financial position and results of operations for the interim periods presented. Certain information and disclosures normally included in the annual financial statements prepared in accordance with GAAP have been condensed or omitted. These condensed interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2013 and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013. The results of operations for the interim periods are not necessarily indicative of the results to be expected for a full year, any other interim periods or any future year or period.

Reverse Stock Split

On June 11, 2013, in connection with its initial public offering (the IPO), the Company effectuated a 1-for-6.986 reverse stock split of its outstanding common stock, which was approved by the Company’s board of directors on June 5, 2013. The reverse stock split resulted in an adjustment to the Series A preferred stock and Series A-1 preferred stock conversion prices to reflect a proportional decrease in the number of shares of common stock to be issued upon conversion. The accompanying financial statements and notes to the financial statements give effect to the reverse stock split for all periods presented. The shares of common stock retained a par value of $0.001 per share. Accordingly, stockholders’ equity reflects the reverse stock split by reclassifying from “common stock” to “Additional paid-in capital” in an amount equal to the par value of the decreased shares resulting from the reverse stock split.

Initial Public Offering

On July 1, 2013, the Company completed its IPO whereby the Company sold 5,000,000 shares of common stock at a price of $14.00 per share. The shares began trading on the Nasdaq Global Market on June 26, 2013. On July 11, 2013, the underwriters exercised their over-allotment option in full and purchased an additional 750,000 shares of common stock at a price of $14.00 per share. The Company received approximately $72.2 million in net proceeds from the IPO, including proceeds from the exercise of the underwriters’ over-allotment option, net of underwriting discounts and commissions and offering expenses. Upon closing of the IPO, all outstanding shares of preferred stock converted into 9,210,999 shares of common stock; and warrants exercisable for convertible preferred stock were automatically converted into warrants exercisable for 277,690 shares of common stock, resulting in the reclassification of the related convertible preferred stock warrant liability of $2.9 million to additional paid-in capital (See Note 4).

The following table summarizes the Company’s capitalization upon closing of its initial public offering:

Total common stock issued as of June 30, 2013		396,414
Conversion of Series A preferred stock into common stock upon closing of IPO		8,244,781
Conversion of Series A-1 preferred stock into common stock upon closing of IPO		966,218
Sales of common stock through IPO		5,000,000
Common stock issued as of July 1, 2013		14,607,413
Issuance of common stock to underwriters due to exercise of over-allotment		750,000
Total common stock issued as of July 11, 2013		15,357,413

Summary of Significant Accounting Policies	3 Months Ended
Summary of Significant Accounting Policies	Mar. 31, 2014
Summary of Significant Accounting Policies
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies There have been no material changes to the significant accounting policies previously disclosed in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2013.

Debt	3 Months Ended
Debt	Mar. 31, 2014
Debt
Debt	3. Debt Convertible Notes In January 2012, the Company issued $6.0 million of 10% convertible promissory notes to certain existing investors for cash. In September and November 2012, the Company issued the aggregate of $9.7 million of 10% convertible promissory notes that mature on September 4, 2013 for cash to certain existing investors. In connection with the September convertible note financing, the Company and the holders of the January 2012 convertible promissory notes agreed to extend the maturity date of the January 2012 notes to September 4, 2013. In February 2013, these convertible promissory notes, with an outstanding principal of $15.7 million and accrued interest of $0.9 million, were amended and then converted into 16,623,092 shares of Series A preferred stock, in accordance with their terms and at their conversion price of $1.00 per share, and following such conversion, the notes were cancelled. The holders of the September convertible promissory notes received the benefit of a deemed conversion price of the September convertible promissory notes that were below the estimated fair value of the Series A convertible preferred stock at the time of their issuance. The fair value of this beneficial conversion feature was estimated to be $0.3 million. The fair value of this beneficial conversion feature was recorded to debt discount and amortized to interest expense using the effective interest method over the term of the convertible promissory notes. As a result of the conversion of the convertible promissory notes into shares of Series A preferred stock in February 2013, the Company recorded an accretion of the beneficial conversion feature of $0, $0.2 million and $0.3 million as interest expense during the three months ended March 31, 2014 and 2013, and the period from inception through March 31, 2014, respectively. In connection with the issuance of the September and the November 2012 convertible promissory notes, the Company issued warrants to purchase shares of Series A preferred stock for an aggregate price of $9,700. The estimated fair value of the warrants at issuance was $0.3 million. The proceeds from the sale of the preferred stock and warrants were allocated with $9.4 million to the convertible promissory notes and $0.3 million to warrants. This resulted in a discount on the convertible promissory notes which was amortized into interest expense, using the effective interest method, over the life of the convertible promissory notes (see Note 4). As a result of the conversion of the convertible promissory notes into shares of Series A preferred stock in February 2013, the Company recorded $0, $0.2 million and $0.3 million of interest expense for the accretion of this discount during the three months ended March 31, 2014 and 2013, and the period from inception through March 31, 2014, respectively. In April 2008, the Company acquired all of the capital stock of Esperion from Pfizer in exchange for a non-subordinated convertible note in the original principal amount of $5.0 million. This convertible promissory note had a maturity date of April 28, 2018. The note bore interest at 8.931% annually, payable semiannually on June 30 and December 31 by adding such unpaid interest to the principal of the note, which would thereafter accrue interest. In May 2013 the Company entered into a stock purchase agreement with Pfizer Inc. and sold 6,750,000 shares of Series A-1 preferred stock at a price of $1.1560 per share, which was the fair value at the transaction date. The purchase price was paid through the cancellation of all outstanding indebtedness, including accrued interest, under the Pfizer convertible promissory note, which had an outstanding balance, including accrued interest, of $7.8 million as of May 29, 2013. The Series A-1 preferred stock issued in connection with this transaction was subsequently converted into 966,218 shares of common stock upon completion of the IPO on July 1, 2013.

Warrants	3 Months Ended
Warrants	Mar. 31, 2014
Warrants
Warrants	4. Warrants In connection with its various financing transactions, the Company issued warrants to purchase shares of preferred stock which had provisions where the underlying issuance was contingently redeemable based on events outside the Company’s control and were recorded as a liability in accordance with ASC 480-10. The warrants were classified as liabilities and were recorded on the Company’s balance sheet at fair value on the date of issuance and marked- to-market on each subsequent reporting period, with the fair value changes recognized in the statement of operations. Subsequent to the pricing of the IPO, the Company estimated the fair values of the warrants at each reporting period using a Black-Scholes option-pricing model, which is based, in part, upon subjective assumptions including but not limited to stock price volatility, the expected life of the warrants, the risk free interest rate and the fair value of the common stock underlying the warrants. The Company estimates the volatility of its stock based on public company peer group historical volatility that is in line with the expected remaining life of the warrants. The risk free interest rate is based on the U.S. Treasury zero-coupon bond for a maturity similar to the expected remaining life of the warrants. The expected remaining life of the warrants is assumed to be equivalent to their remaining contractual term. Prior to the pricing of the IPO, a Monte Carlo valuation model was utilized to estimate the fair value of the warrants based on the probability and timing of future financings. The assumptions used in calculating the estimated fair market value at each reporting period prior to the closing of the Company’s IPO represent the Company’s best estimate, however, do involve inherent uncertainties. The estimated fair value of the warrants was determined using the Monte Carlo valuation model which totaled $0.3 million and was comprised of $0.1 million and $0.2 million as of and for the September and November 2012 financing, respectively, and was recorded as a discount on the related convertible promissory notes and amortized as interest expense over the term of the convertible promissory notes. Inherent in the Monte Carlo valuation model are assumptions related to expected stock-price volatility, expected life and risk-free interest rate. The Company estimates the volatility of its stock based on public company peer group historical volatility that is in line with the expected remaining life of the warrants. The risk-free interest rate is based on the U.S. Treasury zero-coupon bond on the grant date for a maturity similar to the expected remaining life of the warrants. The expected life of the warrants is assumed to be equivalent to their remaining contractual term. The dividend rate is based on the historical rate, which the Company anticipates to remain at zero. The Monte Carlo model was used prior to the closing of the Company’s IPO to appropriately value the potential future exercise price based on various exit scenarios. This requires Level 3 inputs which are based on the Company’s estimates of the probability and timing of potential future financings. Upon the closing of the Company’s IPO, all warrants exercisable for 1,940,000 shares of Series A preferred stock, at an exercise price of $1.00 per share, were automatically converted into warrants exercisable for 277,690 shares of common stock, at an exercise price of $6.99 per share. As a result, the Company concluded the warrants outstanding no longer met the criteria to be classified as liabilities and were reclassified to additional paid-in capital at fair value on the date of reclassification. The 277,690 warrants outstanding as of March 31, 2014 expire in February 2018. During the three months ended March 31, 2014 and 2013, and the period from inception through March 31, 2014, the Company recognized a loss of $0, $42,000 and $2.6 million, respectively, relating to the change in the fair value of the warrant liability.

Commitments and contingencies

3 Months Ended

Mar. 31, 2014

Commitments and contingencies

Commitments and contingencies

5. Commitments and contingencies

In August 2013, the Company entered into the second amendment to the operating lease agreement for its current office and laboratory facility in Plymouth, MI which extended the expiration date of the initial term from October 2013 to April 2014. The Company’s facility lease provides for a fixed monthly rent for the term of the lease and also provides for certain rent adjustments to be paid as determined by the landlord. The operating lease agreement was subsequently amended in May 2014 (See Note 12).

In February 2014, the Company entered into an operating lease agreement for its principal executive offices located in Ann Arbor, Michigan commencing in April 2014 with a term of 63 months. The Company’s lease provides for fixed monthly rent for the term of the lease, with monthly rent increasing every 12 months subsequent to the first three months of the lease, and also provides for certain rent adjustments to be paid as determined by the landlord.

The following table summarizes the Company’s future minimum payments as of March 31, 2014:

	Total		Less than 1 Year		1-3 Years		3-5 Years		More than 5 Years
	(in thousands)
Operating leases	$	535	$	93	$	197	$	209	$	36
Total	$	535	$	93	$	197	$	209	$	36

Investments

3 Months Ended

Mar. 31, 2014

Investments

Investments

6. Investments

The following table summarizes the Company’s cash equivalents and investments:

	March 31, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash equivalents:
Money market funds	$	357	$	—	$	—		$	357
Short-term investments:
U.S. treasury notes	5,617		2		—			5,619
U.S. government agency securities	2,446		—		(1		)	2,445
Long-term investments:
Certificates of deposit	237		—		—			237
U.S. treasury notes	5,526		7		—			5,533
U.S. government agency securities	5,763		—		(5		)	5,758
Total	$	19,946	$	9	$	(6	)	$	19,949

	December 31, 2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash equivalents:
Money market funds	$	5,356	$	—	$	—		$	5,356
Short-term investments:
U.S. treasury notes	2,071		—		—			2,071
U.S. government agency securities	1,454		—		—			1,454
Long-term investments:
Certificates of deposit	238		—		—			238
U.S. treasury notes	9,116		3		(2		)	9,117
U.S. government agency securities	8,187		1		(5		)	8,183
Total	$	26,422	$	4	$	(7	)	$	26,419

At March 31, 2014 and December 31, 2013, remaining contractual maturities of available for sale investments classified as current on the balance sheet were less than 12 months, and remaining contractual maturities of available for sale investments classified as long term were less than two years.

There were no unrealized gains or losses on investments reclassified from accumulated other comprehensive income to other income (expense) in the Statement of Operations during the three months ended March 31, 2014.

Fair Value Measurements

3 Months Ended

Mar. 31, 2014

Fair Value Measurements

Fair Value Measurements

7. Fair Value Measurements

The Company follows accounting guidance that emphasizes that fair value is a market-based measurement, not an entity-specific measurement. Fair value is defined as “the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants at the measurement date.” Fair value measurements are defined on a three level hierarchy:

Level 1 inputs:		Quoted prices for identical assets or liabilities in active markets;

Level 2 inputs:		Observable inputs other than Level 1 prices, such as quoted market prices for similar assets or liabilities or other inputs that are observable or can be corroborated by market data; and

Level 3 inputs:		Unobservable inputs that are supported by little or no market activity and require the reporting entity to develop assumptions that market participants would use when pricing the asset or liability.

The following table presents the Company’s financial assets and liabilities that have been measured at fair value on a recurring basis:

Description	Total		Level 1		Level 2		Level 3
	(in thousands)
March 31, 2014
Assets:
Money market funds	$	357	$	357	$	—	$	—
Available for sale securities:
Certificates of deposit	237		237		—		—
U.S. treasury notes	11,152		11,152		—		—
U.S. government agency securities	8,203		—		8,203		—
Total assets at fair value	$	19,949	$	11,746	$	8,203	$	—
December 31, 2013
Assets:
Money market funds	$	5,356	$	5,356	$	—	$	—
Available for sale securities:
Certificates of deposit	238		238		—		—
U.S. treasury notes	11,188		11,188		—		—
U.S. government agency securities	9,637		—		9,637		—
Total assets at fair value	$	26,419	$	16,782	$	9,637	$	—

There were no transfers between Levels 1, 2 or 3 during the three months ended March 31, 2014.

Fair Value Measurements on a Nonrecurring Basis

In addition to items that are measured at fair value on a recurring basis, the Company also measures assets held for sale at the lower of its carrying amount or fair value on a nonrecurring basis. During the three months ended March 31, 2014 and 2013, and the period from inception through March 31, 2014, the Company recognized impairment expense of $0, $27,000, and $0.2 million, respectively, related to the assets held for sale. The fair value of assets held for sale was estimated using a market approach, considering the estimated fair value for other comparable equipment which are Level 3 inputs.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

Convertible Preferred Stock and Stockholders' Equity	3 Months Ended
Convertible Preferred Stock and Stockholders' Equity	Mar. 31, 2014
Convertible Preferred Stock and Stockholders' Equity
Convertible Preferred Stock and Stockholders' Equity	8. Convertible Preferred Stock and Stockholders’ Equity On April 19, 2013, the Company issued and sold an aggregate of 17,000,000 shares of Series A preferred stock at a price of $1.00 per share for proceeds of $16.9 million, which is net of issuance costs of $0.1 million, to funds affiliated with Longitude Capital and certain existing investors. Each share of Series A preferred stock issued in the financing was convertible into 0.143 shares of common stock as of June 30, 2013. Upon the closing of the financing, Patrick Enright of Longitude Capital became a member of the board of directors. On May 29, 2013, the Company entered into a stock purchase agreement with Pfizer Inc. and issued and sold 6,750,000 shares of Series A-1 preferred stock at a price of $1.1560 per share. The purchase price was paid through the cancellation of all outstanding indebtedness, including accrued interest, under the Pfizer convertible promissory note, which had an aggregate balance, including accrued interest, of $7.8 million as of May 29, 2013. Each share of Series A-1 preferred stock issued in the agreement was convertible into 0.143 shares of common stock upon the closing of the Company’s IPO. Upon the closing of the Company’s IPO on July 1, 2013, all of the outstanding shares of convertible preferred stock were converted into 9,210,999 shares of common stock. As of March 31, 2014, the Company did not have any convertible preferred stock issued or outstanding.

Stock Compensation

3 Months Ended

Mar. 31, 2014

Stock Compensation

Stock Compensation

9. Stock Compensation

2013 Stock Option and Incentive Plan

On June 7, 2013, the Company’s stockholders approved the 2013 Stock Option and Incentive Plan (the 2013 Plan), which became effective on June 25, 2013. The number of shares of stock reserved and available for issuance under the 2013 Plan is the sum of (i) 1,100,000, plus (ii) 54,129 shares originally reserved under the Company’s 2008 Incentive Stock Option and Restricted Stock Plan (the 2008 Plan) that became available for issuance under the 2013 Plan upon completion of the Company’s initial public offering, plus (iii) the shares underlying any awards granted under the 2008 Plan that are forfeited, canceled, held back upon the exercise of an option or settlement of an award to cover the exercise price or tax withholding, reacquired by the Company prior to vesting, satisfied without the issuance of stock or otherwise terminated (other than be exercise). Additionally, on January 1, 2014 and each January 1 thereafter, the number of shares reserved and available for issuance under the 2013 Plan shall be cumulatively increased by two and a half percent of the number of shares issued and outstanding on the immediately preceding December 31 or such lesser number of shares as determined by the plan administrator. On January 1, 2014, the number of shares of stock reserved and available for issuance under the 2013 Plan increased by 383,935 shares.

Under the 2013 Plan the vesting of options granted or restricted awards given will be determined individually with each option grant. Stock options have a 10 year life and expire if not exercised within that period, or if not exercised within 90 days of cessation of employment with the Company.

The following table summarizes the activity relating to the Company’s options to purchase common stock for the three months ended March 31, 2014:

	Number of Options		Weighted-Average Price Per Share		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
						(in thousands)
Outstanding at December 31, 2013	1,401,101		$	9.59	8.95	$	7,755
Granted	67,000		$	15.34
Forfeited or expired	(2,871	)	$	1.54
Exercised	(36,813	)	$	1.42
Outstanding at March 31, 2014	1,428,417		$	10.09	8.95	$	8,348

The following table summarizes information about the Company’s stock option plan as of March 31, 2014:

	Number of Options	Weighted-Average Price Per Share		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
					(in thousands)
Vested and expected to vest at March 31, 2014	1,367,576	$	10.00	8.93	$	8,107
Exercisable at March 31, 2014	615,061	$	3.79	8.41	$	7,075

As of March 31, 2014, there was approximately $7.6 million of unrecognized compensation cost related to unvested options, adjusted for forfeitures, which will be recognized over a weighted-average period of approximately 3.16 years.

Income Taxes	3 Months Ended
Income Taxes	Mar. 31, 2014
Income Taxes
Income Taxes	10. Income Taxes There was no provision for income taxes for the three months ended March 31, 2014 and 2013 because the Company has incurred operating losses since inception. At March 31, 2014, the Company has concluded that it is more likely than not that the Company will not realize the benefit of its deferred tax assets due to its history of losses. Accordingly, the net deferred tax assets have been fully reserved.

Net Loss Per Common Share

3 Months Ended

Mar. 31, 2014

Net Loss Per Common Share

Net Loss Per Common Share

11. Net Loss Per Common Share

Basic net loss per share is calculated by dividing net loss by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is computed by dividing net loss by the weighted-average number of common stock equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, warrants for common stock, stock options and unvested restricted stock are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive. Interest expense for convertible debt that is dilutive is added back to net income in the calculation of diluted net loss per share.

The shares outstanding at the end of the respective periods presented below, after giving effect for the 1-for-6.986 reverse stock split, were excluded from the calculation of diluted net loss per share due to their anti-dilutive effect:

	March 31, 2014	December 31, 2013

Warrants for common stock	277,690	277,690
Common shares under option	1,428,417	1,401,101
Unvested restricted stock	14,915	16,703
Total potential dilutive shares	1,721,022	1,695,494

Subsequent Events	3 Months Ended
Subsequent Events	Mar. 31, 2014
Subsequent Events
Subsequent Events	12. Subsequent Events In May 2014, the Company entered into the third amendment to the operating lease agreement for its laboratory facility in Plymouth, Michigan. The amendment provides in part that (i) the expiration date of the term of the lease is extended from April 2014 to April 2017, (ii) the rentable laboratory space is adjusted to 3,045 square feet, (iii) the Company’s proportionate share of the landlord’s expenses and taxes is adjusted to 7.40% (iv) the Company may exercise its option to renew the lease for one term of three years through written notice to the landlord by February 2017 and (v) the annual base rent under the lease is decreased to approximately $37,000, subject to increase and adjustments provided in the lease.

The Company and Basis of Presentation (Policies)

3 Months Ended

Mar. 31, 2014

The Company and Basis of Presentation

Basis of Presentation

Basis of Presentation

Reverse Stock Split

Reverse Stock Split

Initial Public Offering

Initial Public Offering

The following table summarizes the Company’s capitalization upon closing of its initial public offering:

Total common stock issued as of June 30, 2013		396,414
Conversion of Series A preferred stock into common stock upon closing of IPO		8,244,781
Conversion of Series A-1 preferred stock into common stock upon closing of IPO		966,218
Sales of common stock through IPO		5,000,000
Common stock issued as of July 1, 2013		14,607,413
Issuance of common stock to underwriters due to exercise of over-allotment		750,000
Total common stock issued as of July 11, 2013		15,357,413

The Company and Basis of Presentation (Tables)

3 Months Ended

Mar. 31, 2014

The Company and Basis of Presentation

Summary of the Company's capitalization upon closing of its initial public offering

Total common stock issued as of June 30, 2013		396,414
Conversion of Series A preferred stock into common stock upon closing of IPO		8,244,781
Conversion of Series A-1 preferred stock into common stock upon closing of IPO		966,218
Sales of common stock through IPO		5,000,000
Common stock issued as of July 1, 2013		14,607,413
Issuance of common stock to underwriters due to exercise of over-allotment		750,000
Total common stock issued as of July 11, 2013		15,357,413

Commitments and contingencies (Tables)

3 Months Ended

Mar. 31, 2014

Commitments and contingencies

Summary of future minimum payments

The following table summarizes the Company’s future minimum payments as of March 31, 2014:

	Total		Less than 1 Year		1-3 Years		3-5 Years		More than 5 Years
	(in thousands)
Operating leases	$	535	$	93	$	197	$	209	$	36
Total	$	535	$	93	$	197	$	209	$	36

Investments (Tables)

3 Months Ended

Mar. 31, 2014

Investments

Summary of the Company's cash equivalents and investments

	March 31, 2014
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash equivalents:
Money market funds	$	357	$	—	$	—		$	357
Short-term investments:
U.S. treasury notes	5,617		2		—			5,619
U.S. government agency securities	2,446		—		(1		)	2,445
Long-term investments:
Certificates of deposit	237		—		—			237
U.S. treasury notes	5,526		7		—			5,533
U.S. government agency securities	5,763		—		(5		)	5,758
Total	$	19,946	$	9	$	(6	)	$	19,949

	December 31, 2013
	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
	(in thousands)
Cash equivalents:
Money market funds	$	5,356	$	—	$	—		$	5,356
Short-term investments:
U.S. treasury notes	2,071		—		—			2,071
U.S. government agency securities	1,454		—		—			1,454
Long-term investments:
Certificates of deposit	238		—		—			238
U.S. treasury notes	9,116		3		(2		)	9,117
U.S. government agency securities	8,187		1		(5		)	8,183
Total	$	26,422	$	4	$	(7	)	$	26,419

Fair Value Measurements (Tables)

3 Months Ended

Mar. 31, 2014

Fair Value Measurements

Schedule of the Company's financial assets and liabilities that have been measured at fair value on a recurring basis

Description	Total		Level 1		Level 2		Level 3
	(in thousands)
March 31, 2014
Assets:
Money market funds	$	357	$	357	$	—	$	—
Available for sale securities:
Certificates of deposit	237		237		—		—
U.S. treasury notes	11,152		11,152		—		—
U.S. government agency securities	8,203		—		8,203		—
Total assets at fair value	$	19,949	$	11,746	$	8,203	$	—
December 31, 2013
Assets:
Money market funds	$	5,356	$	5,356	$	—	$	—
Available for sale securities:
Certificates of deposit	238		238		—		—
U.S. treasury notes	11,188		11,188		—		—
U.S. government agency securities	9,637		—		9,637		—
Total assets at fair value	$	26,419	$	16,782	$	9,637	$	—

Stock Compensation (Tables)

3 Months Ended

Mar. 31, 2014

Stock Compensation

Summary of activity relating to the Company's options to purchase common stock

	Number of Options		Weighted-Average Price Per Share		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
						(in thousands)
Outstanding at December 31, 2013	1,401,101		$	9.59	8.95	$	7,755
Granted	67,000		$	15.34
Forfeited or expired	(2,871	)	$	1.54
Exercised	(36,813	)	$	1.42
Outstanding at March 31, 2014	1,428,417		$	10.09	8.95	$	8,348

Summary of information about the stock option plan

	Number of Options	Weighted-Average Price Per Share		Weighted-Average Remaining Contractual Term (Years)	Aggregate Intrinsic Value
					(in thousands)
Vested and expected to vest at March 31, 2014	1,367,576	$	10.00	8.93	$	8,107
Exercisable at March 31, 2014	615,061	$	3.79	8.41	$	7,075

Net Loss Per Common Share (Tables)

3 Months Ended

Mar. 31, 2014

Net Loss Per Common Share

Schedule of anti-dilutive securities excluded from the calculation of diluted net loss per share

	March 31, 2014	December 31, 2013

Warrants for common stock	277,690	277,690
Common shares under option	1,428,417	1,401,101
Unvested restricted stock	14,915	16,703
Total potential dilutive shares	1,721,022	1,695,494

The Company and Basis of Presentation (Details) $ / shares in Units, $ in Thousands				74 Months Ended
	Jul. 11, 2013 USD ($) $ / shares	Jul. 02, 2013 USD ($) $ / shares shares	Jun. 11, 2013 $ / shares	Mar. 31, 2014 USD ($) $ / shares	Dec. 31, 2013 $ / shares
Reverse Stock Split
Reverse stock split ratio of outstanding common stock			0.1431
Par value of common stock (in dollars per share) \| $ / shares			$ 0.001	$ 0.001	$ 0.001
Initial Public Offering
Net proceeds from the IPO, including proceeds from the exercise of the underwriters' over-allotment option				$ 72,194
Common stock \| Warrant
Initial Public Offering
Warrants exercisable into common stock (in shares) \| shares		277,690
Initial Public Offering
Reverse Stock Split
Reverse stock split ratio of outstanding common stock			0.1431
Initial Public Offering
Original issue price (in dollars per share) \| $ / shares		$ 14.00
Net proceeds from the IPO, including proceeds from the exercise of the underwriters' over-allotment option	$ 72,200
Initial Public Offering \| Common stock
Initial Public Offering
Number of shares of convertible preferred stock converted into common stock \| shares		9,210,999
Initial Public Offering \| Common stock \| Additional paid-in capital
Initial Public Offering
Reclassification of convertible preferred stock warrant liability to additional paid-in capital		$ 2,900
Initial Public Offering \| Convertible preferred stock \| Warrant liabilities
Initial Public Offering
Reclassification of convertible preferred stock warrant liability to additional paid-in capital		$ (2,900)
Over-allotment option
Initial Public Offering
Original issue price (in dollars per share) \| $ / shares	$ 14.00

The Company and Basis of Presentation (Details 2) - shares	Jul. 11, 2013	Jul. 02, 2013
Movement in Company's capitalization upon closing of initial public offering
Balance (in shares)	396,414	396,414
Balance (in shares)	15,357,413	14,607,413
Initial Public Offering \| Series A preferred stock
Movement in Company's capitalization upon closing of initial public offering
Conversion of preferred stock into common stock upon closing of IPO (in shares)		8,244,781
Initial Public Offering \| Series A-1 preferred stock
Movement in Company's capitalization upon closing of initial public offering
Conversion of preferred stock into common stock upon closing of IPO (in shares)		966,218
Initial Public Offering \| Common stock
Movement in Company's capitalization upon closing of initial public offering
Conversion of preferred stock into common stock upon closing of IPO (in shares)		9,210,999
Common stock sold (in shares)		5,000,000
Over-allotment option
Movement in Company's capitalization upon closing of initial public offering
Common stock sold (in shares)	750,000

Debt (Details) - USD ($)		1 Months Ended	3 Months Ended			74 Months Ended
Debt (Details) - USD ($)	Jul. 02, 2013	Feb. 28, 2013	Mar. 31, 2014	Mar. 31, 2013	Nov. 30, 2012	Mar. 31, 2014	May 29, 2013	Apr. 19, 2013	Jan. 31, 2012	Apr. 28, 2008
Series A preferred stock
Debt
Share price of preferred stock (in dollars per share)								$ 1.00
10% Convertible promissory notes \| Series A preferred stock
Debt
Aggregate principal amount		$ 15,700,000
Accrued interest		$ 900,000
Conversion of convertible promissory notes into Series A preferred stock (in shares)		16,623,092
Conversion price (in dollars per share)		$ 1.00
Short term convertible notes issued January 2012
Debt
Aggregate principal amount									$ 6,000,000
Interest rate (as a percent)									10.00%
Short term convertible notes issued September and November 2012
Debt
Aggregate principal amount					$ 9,700,000
Interest rate (as a percent)					10.00%
Short term borrowings with related parties, net of debt discount					$ 9,400,000
Short term convertible notes issued September and November 2012 \| Warrant \| Estimated fair value
Debt
Estimated fair value of warrants					300,000
Short term convertible notes issued September and November 2012 \| Series A preferred stock \| Warrant
Debt
Aggregate purchase price of warrants					$ 9,700
Short term convertible notes issued September 2012
Debt
Fair value of beneficial conversion feature		$ 300,000
Short term convertible notes issued September 2012 \| Interest Expense
Debt
Amortization of debt discount and beneficial conversion			$ 0	$ 200,000		$ 300,000
Pfizer Note
Debt
Aggregate principal amount										$ 5,000,000
Interest rate (as a percent)										8.931%
Outstanding principal amount							$ 7,800,000
Pfizer Note \| Series A-1 preferred stock
Debt
Preferred stock, shares issued							6,750,000
Share price of preferred stock (in dollars per share)							$ 1.1560
Number of shares of preferred stock converted into shares of common stock	966,218

Warrants (Details) $ in Thousands	3 Months Ended		74 Months Ended
Warrants (Details) $ in Thousands	Mar. 31, 2014 USD ($) shares	Mar. 31, 2013 USD ($)	Mar. 31, 2014 USD ($) shares	Jul. 02, 2013 $ / shares shares	Nov. 30, 2012 USD ($)	Sep. 30, 2012 USD ($)
Warrants
Loss related to the change in the fair value of the warrant liability	$ 0	$ 42	$ 2,554
Warrant
Warrants
Number of shares of common stock to be purchased against outstanding warrants \| shares	277,690		277,690
Warrant \| Estimated fair value \| Short term convertible notes issued September and November 2012
Warrants
Estimated fair value					$ 300
Warrant \| Estimated fair value \| Short term convertible notes issued September 2012
Warrants
Estimated fair value						$ 100
Warrant \| Estimated fair value \| Short term convertible notes issued November 2012
Warrants
Estimated fair value					200
Series A preferred stock warrant
Warrants
Warrants exercisable into stock (in shares) \| shares				1,940,000
Exercise price (in dollars per share) \| $ / shares				1.00
Series A preferred stock warrant \| Estimated fair value \| Short term convertible notes issued September and November 2012
Warrants
Estimated fair value					$ 300
Common stock \| Warrant
Warrants
Warrants exercisable into stock (in shares) \| shares				277,690
Share price of common stock (in dollars per share) \| $ / shares				$ 6.99

Commitments and contingencies (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Feb. 28, 2014	Mar. 31, 2014
Commitments and contingencies
Term period of lease	63 months
Operating lease period for monthly rent increasing in fixed monthly rent		12 months
Operating lease period after which monthly rent increase		3 months
Operating leases
Total		$ 535
Less than 1 Year		93
1-3 Years		197
3-5 Years		209
More than 5 Years		$ 36

Investments (Details) - USD ($) $ in Thousands	3 Months Ended		74 Months Ended
Investments (Details) - USD ($) $ in Thousands	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Dec. 31, 2013
Cash equivalents and investments
Gross Unrealized Gains	$ 9		$ 9	$ 4
Gross Unrealized Losses	(6)		(6)	(7)
Total, Amortized Cost	19,946		19,946	26,422
Total, Estimated Fair Value	19,949		19,949	26,419
Unrealized gains or losses	16	$ (25)	292
Reclassification out of accumulated other comprehensive income
Cash equivalents and investments
Unrealized gains or losses	0
Short-term investments \| U.S. treasury notes
Cash equivalents and investments
Investments, Amortized Cost	5,617		5,617	2,071
Gross Unrealized Gains	2		2
Investments, Estimated Fair Value	5,619		5,619	2,071
Short-term investments \| U.S. government agency securities
Cash equivalents and investments
Investments, Amortized Cost	2,446		2,446	1,454
Gross Unrealized Losses	(1)		(1)
Investments, Estimated Fair Value	2,445		2,445	1,454
Long-term investments \| U.S. treasury notes
Cash equivalents and investments
Investments, Amortized Cost	5,526		5,526	9,116
Gross Unrealized Gains	7		7	3
Gross Unrealized Losses				(2)
Investments, Estimated Fair Value	5,533		5,533	9,117
Long-term investments \| U.S. government agency securities
Cash equivalents and investments
Investments, Amortized Cost	5,763		5,763	8,187
Gross Unrealized Gains				1
Gross Unrealized Losses	(5)		(5)	(5)
Investments, Estimated Fair Value	5,758		5,758	8,183
Money market funds
Cash equivalents and investments
Cash equivalents, Estimated Fair Value	357		357	5,356
Investments, Amortized Cost	357		357	5,356
Certificates of deposit \| Long-term investments
Cash equivalents and investments
Investments, Amortized Cost	237		237	238
Investments, Estimated Fair Value	$ 237		$ 237	$ 238

Fair Value Measurements (Details) - USD ($) $ in Thousands	3 Months Ended
Fair Value Measurements (Details) - USD ($) $ in Thousands	Mar. 31, 2014	Dec. 31, 2013
Assets:
Total, Estimated Fair Value	$ 19,949	$ 26,419
Transfer of assets between levels	0
Recurring fair value measurement \| Level 1
Assets:
Money market fund	357	5,356
Total, Estimated Fair Value	11,746	16,782
Recurring fair value measurement \| Level 1 \| U.S. treasury notes
Assets:
Available for sale securities	11,152	11,188
Recurring fair value measurement \| Level 1 \| Certificates of deposit
Assets:
Available for sale securities	237	238
Recurring fair value measurement \| Level 2
Assets:
Total, Estimated Fair Value	8,203	9,637
Recurring fair value measurement \| Level 2 \| U.S. government agency securities
Assets:
Available for sale securities	8,203	9,637
Recurring fair value measurement \| Total
Assets:
Money market fund	357	5,356
Total, Estimated Fair Value	19,949	26,419
Recurring fair value measurement \| Total \| U.S. treasury notes
Assets:
Available for sale securities	11,152	11,188
Recurring fair value measurement \| Total \| U.S. government agency securities
Assets:
Available for sale securities	8,203	9,637
Recurring fair value measurement \| Total \| Certificates of deposit
Assets:
Available for sale securities	$ 237	$ 238

Fair Value Measurements (Details 2) - USD ($)	3 Months Ended		74 Months Ended
Fair Value Measurements (Details 2) - USD ($)	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014
Nonrecurring fair value measurement
Fair Value Measurements on a Nonrecurring Basis
Impairment loss related to the assets held for sale	$ 0	$ 27,000	$ 200,000

Convertible Preferred Stock and Stockholders' Equity (Details) $ / shares in Units, $ in Thousands			74 Months Ended
	Jul. 02, 2013 $ / shares shares	Apr. 19, 2013 USD ($) $ / shares shares	Mar. 31, 2014 USD ($)	May 29, 2013 USD ($) $ / shares shares
Convertible preferred stock and stockholders' deficit
Proceeds from issuance of preferred stock, net of issuance costs \| $			$ 40,799
Pfizer note
Convertible preferred stock and stockholders' deficit
Outstanding principal amount \| $				$ 7,800
Common stock \| Common stock warrant
Convertible preferred stock and stockholders' deficit
Share price of preferred stock (in dollars per share) \| $ / shares	$ 6.99
Series A preferred stock
Convertible preferred stock and stockholders' deficit
Preferred stock, shares authorized		17,000,000
Share price of preferred stock (in dollars per share) \| $ / shares		$ 1.00
Proceeds from issuance of preferred stock, net of issuance costs \| $		$ 16,900
Stock issuance costs \| $		$ 100
Conversion rate		0.143
Series A-1 preferred stock \| Pfizer note
Convertible preferred stock and stockholders' deficit
Preferred stock, shares authorized				6,750,000
Share price of preferred stock (in dollars per share) \| $ / shares				$ 1.1560
Conversion rate				0.143
Number of shares of convertible preferred stock converted into common stock	966,218
IPO \| Common stock
Convertible preferred stock and stockholders' deficit
Number of shares of convertible preferred stock converted into common stock	9,210,999
IPO \| Series A preferred stock
Convertible preferred stock and stockholders' deficit
Number of shares of convertible preferred stock converted into common stock	8,244,781
IPO \| Series A-1 preferred stock
Convertible preferred stock and stockholders' deficit
Number of shares of convertible preferred stock converted into common stock	966,218

Stock Compensation (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended	12 Months Ended
	Jan. 02, 2014	Jun. 25, 2013	Mar. 31, 2014	Dec. 31, 2013
Number of Options
Outstanding at the beginning of period (in shares)	1,401,101		1,401,101
Granted (in shares)			67,000
Forfeited or expired (in shares)			(2,871)
Exercised (in shares)			(36,813)
Outstanding at the end of the period (in shares)			1,428,417	1,401,101
Weighted-Average Price Per Share
Outstanding at the beginning of period (in dollars per share)	$ 9.59		$ 9.59
Granted (in dollars per share)			15.34
Forfeited or expired (in dollars per share)			1.54
Exercised (in dollars per share)			1.42
Outstanding at the end of the period (in dollars per share)			$ 10.09	$ 9.59
Weighted-Average Remaining Contractual Term (Years)
Outstanding at the end of the period			8 years 11 months 12 days	8 years 11 months 12 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)			$ 8,348	$ 7,755
Information about the stock option plan
Number of Options, vested and expected to vest (in shares)			1,367,576
Number of Options, exercisable (in shares)			615,061
Weighted-Average Price Per Share, vested and expected to vest (in dollars per share)			$ 10.00
Weighted-Average Price Per Share, exercisable (in dollars per share)			$ 3.79
Weighted-Average Remaining Contractual Term, vested and expected to vest			8 years 11 months 5 days
Weighted-Average Remaining Contractual Term, exercisable			8 years 4 months 28 days
Aggregate Intrinsic Value, vested and expected to vest (in dollars)			$ 8,107
Aggregate Intrinsic Value, exercisable (in dollars)			7,075
Additional disclosures
Unrecognized compensation cost (in dollars)			$ 7,600
Weighted-average period over which remaining unrecognized compensation cost will be recognized			3 years 1 month 28 days
2013 Plan
Stock compensation
Shares reserved and approved for issuance		1,100,000
Shares reserved under previous plan and subsequently transferred to new plan		54,129
Percentage of increase in the number of shares reserved and available for issuance		2.50%
Increase in the number of shares of stock reserved and available for issuance	383,935
Expiration period			10 years
Period from cessation of employment within which options expire if not exercised			90 days
2008 Incentive Stock Option and Restricted Stock Plan
Stock compensation
Shares reserved under previous plan and subsequently transferred to new plan		54,129

Income Taxes (Details) - USD ($)	3 Months Ended
Income Taxes (Details) - USD ($)	Mar. 31, 2014	Mar. 31, 2013
Income Taxes
Provision for income taxes	$ 0	$ 0

Net Loss Per Common Share (Details)		3 Months Ended	12 Months Ended
Net Loss Per Common Share (Details)	Jun. 11, 2013	Mar. 31, 2014 shares	Dec. 31, 2013 shares
Net Loss Per Common Share
Reverse stock split ratio of shares outstanding	0.1431
Net Loss Per Common Share
Total potential dilutive shares		1,721,022	1,695,494
Warrants for common stock
Net Loss Per Common Share
Total potential dilutive shares		277,690	277,690
Common shares under option
Net Loss Per Common Share
Total potential dilutive shares		1,428,417	1,401,101
Unvested restricted stock
Net Loss Per Common Share
Total potential dilutive shares		14,915	16,703

Subsequent Events (Details) - Subsequent event - Third amendment to the operating lease agreement for laboratory facility in Plymouth, Michigan	1 Months Ended
	May 31, 2014 USD ($) ft² item
Subsequent events
Adjusted rentable laboratory space (in square feet) \| ft²	3,045
Adjusted proportionate share of landlord's expenses and taxes (as a percent)	7.40%
Number of terms which Company may exercise to renew lease \| item	1
Lease renewal term	3 years
Annual base rent under new lease agreement \| $	$ 37,000